The best pokemon?

Hello all, I randomly got a thought that if your team was allowed to only use one pokemon, like 5 pikachus in a team or 5 cindrace in a team (I know how awful that sounds😭), so which pokemon would you use, like the same pokemon has to attack, play a tank, cc, secure ray and heal if it can? Or even if it does not do all of this, tell me a pokemon which will be dominant in this format.